When is a DEXA (Dual-Energy X-ray Absorptiometry) scan recommended?

DEXA Scan Recommendations

Primary Screening Guidelines

All women aged 65 years and older should undergo routine DEXA screening regardless of risk factors, and all men aged 70 years and older should undergo routine DEXA screening. 1, 2, 3

Age-Based Screening Thresholds

• Women ≥65 years: Universal screening recommended 1, 2, 3
• Men ≥70 years: Universal screening recommended 1, 2, 3
• Postmenopausal women <65 years: Screen only if elevated risk based on clinical assessment or FRAX 10-year major osteoporotic fracture risk ≥9.3% 2, 3
• Men <70 years: Screen only if specific risk factors present 2, 3

High-Risk Populations Requiring Earlier Screening (Any Age)

The following conditions warrant DEXA screening regardless of age:

Fracture and Structural Changes

• Previous fragility fracture at any age 1, 2, 3
• Historical height loss ≥1.5 inches (≥4 cm) 1, 2
• Prospective height loss ≥0.8 inch 1
• Kyphosis 1, 2
• Acute onset back pain with osteoporosis risk factors 1

Medication-Related Risk Factors

• Long-term glucocorticoid therapy (≥5 mg prednisone daily for ≥3 months) 1, 2, 3
• Androgen deprivation therapy for prostate cancer 1, 2, 3
• Other medications associated with bone loss 2, 3

Medical Conditions

• Hyperparathyroidism 1, 2, 3
• Hypogonadism (including Klinefelter syndrome) 2, 3, 4
• Chronic alcoholism 3
• Spinal cord injury (scan as soon as medically stable) 1, 2, 3
• Chronic inflammatory diseases 3
• Malabsorption 5
• HIV infection (postmenopausal women and men ≥50 years) 3
• Type 2 diabetes (note: BMD may underestimate fracture risk) 1

Anatomic Sites to Scan

Standard DEXA should include lumbar spine (L2-4) and bilateral hips (total hip and femoral neck). 1, 6

Special Populations Requiring Additional Sites

• Spinal cord injury patients: Total hip, proximal tibia, and distal femur (requires specialized DXA machines) 1, 2

Vertebral Fracture Assessment (VFA) Indications

VFA should be performed during the same DEXA session for:

• Women aged ≥70 years or men aged ≥80 years with T-score ≤-1.0 at any site 1, 2
• Men aged 70-79 years with T-score ≤-1.5 at lumbar spine, total hip, or femoral neck 1, 2
• Women aged ≥65 years with T-score ≤-1.0 at femoral neck 1, 2
• Historical height loss >4 cm 2
• Self-reported but undocumented prior vertebral fracture 2
• Oral glucocorticoid therapy ≥5 mg prednisone daily for ≥3 months 2

Follow-Up Scanning Intervals

Based on Initial Results

• Normal BMD: Repeat in 2-3 years, though intervals up to 4-8 years may be appropriate for low-risk individuals 2, 3, 4
• Osteopenia (T-score -1.0 to -2.4): Repeat in 2-3 years if T-score >-2.0; no routine repeat needed unless new risk factors develop 2
• Osteoporosis or on treatment: Repeat in 1-2 years to monitor treatment effectiveness 1, 2, 3, 4

Special Populations

• Spinal cord injury: Follow-up at 1-2 year intervals 1, 2, 3
• Prostate cancer on ADT: Clinical assessment at 1-2 year intervals 1
• HIV patients: Repeat every 2-5 years depending on proximity to treatment thresholds 3
• Glucocorticoid therapy: Shorter intervals (1-2 years) due to accelerated bone loss 2
• Klinefelter syndrome: Every 2 years if osteopenia/osteoporosis present, every 2-3 years if osteopenic, every 2-5 years if normal (closer to 2-year intervals preferred) 4

Treatment Monitoring

• Bisphosphonate therapy: Monitor prior to temporary cessation and during planned interruption 1
• Minimum interval: Never repeat scans <1 year apart; minimum 2 years needed to reliably measure BMD change 2

Diagnostic Thresholds

• Osteoporosis: T-score ≤-2.5 at lumbar spine, femoral neck, or total hip 1, 5, 6
• Glucocorticoid-induced osteoporosis: Consider treatment at T-score <-1.5 (fractures occur at higher BMD levels than postmenopausal osteoporosis) 5
• Vertebral fractures: Generally diagnostic of osteoporosis even if BMD not in osteoporotic range 5

Special Considerations

Transgender Individuals

• Calculate Z-score using reference data conforming to gender identity 1, 2, 3
• Post-pubertal transgender youth on gonadotropin-releasing hormone without sex steroid therapy are at risk for decreasing bone density 2, 3
• Consider referral to specialized center 1

FRAX Utilization

• Use "secondary osteoporosis" option for men with prostate cancer on ADT when femoral neck BMD unavailable 1, 3
• Note: Secondary osteoporosis variable only affects FRAX when BMD not entered 1

Critical Pitfalls to Avoid

• Do not delay screening in high-risk individuals (chronic alcoholism, Klinefelter syndrome, glucocorticoid therapy) until age 65/70 thresholds 3, 4
• Do not repeat scans <2 years apart in stable patients with normal BMD—this provides no clinical benefit and exposes patients to unnecessary radiation 2
• Do not assume obesity protects against osteoporosis when other major risk factors present 3
• Do not overlook new risk factors at clinical encounters that might warrant earlier repeat testing 2
• Do not use peripheral DXA results with WHO diagnostic criteria—these devices cannot be interpreted using standard thresholds 6
• Do not delay treatment for secondary fracture prevention if fracture occurs, even if awaiting DEXA results 1
• Do not fail to perform comprehensive metabolic workup in high-risk patients (calcium, phosphate, alkaline phosphatase, 25-hydroxyvitamin D, liver function tests) 3